#' Get map from Baidu API
#'
#' Take in coordiantes and return the location
#'
#' @param location a vector a or matrix contains longtitude and latitude of the center of the map, or a character refers to the address
#' @param width width of the map
#' @param height height of the map
#' @param zoom map zoom, an integer from 3 (continent) to 21 (building), default value 10 (city)
#' @param scale multiplicative factor for the number of pixels returned. possible values are 2 or anything else.
#' @param color "color" or "bw", color or black-and-white
#' @param messaging logical. whether to print the download messages.
#' @return A ggmap object. a map image as a 2d-array of colors as hexadecimal strings representing pixel fill values.
#' @export
#' @importFrom png readPNG
#' @importFrom RgoogleMaps XY2LatLon
#' @importFrom ggmap ggmap
#' @examples
#'
#' \dontrun{
#' library(ggmap)
#' ## Beijing
#' p <- getBaiduMap(c(116.39565, 39.92999))
#' ggmap(p)
#'
#' p <- getBaiduMap('beijing') # the same
#' ggmap(p)
#'
#' ## black-and-white
#' p <- getBaiduMap(color='bw')
#' ggmap(p)
#'
#' ## do not print messages
#' p <- getBaiduMap(messaging = F)
#' }
getBaiduMap = function(location, width=400, height = 400, zoom=10,
scale=2, color = "color", messaging = TRUE,
map_ak = ''){
if (map_ak == '' && is.null(getOption('baidumap.key'))){
stop(Notification)
}else{
map_ak = ifelse(map_ak == '', getOption('baidumap.key'), map_ak)
}
## location
if (is.character(location) && length(location) == 1){
location_cor = getCoordinate(location, formatted=T)
} else if (length(location == 2)){
location_cor = location
} else{
stop('Wrong address!')
}
lon = location_cor[1];
lat = location_cor[2];
## set url
url_head = "http://api.map.baidu.com/staticimage?"
url = paste0(url_head, "width=", width, "&height=", height, "¢er=",
lon, ",", lat, "&zoom=", zoom)
if (scale == 2) url = paste0(url, "&scale=2")
## download image
if (!'baiduMapFileDrawer' %in% list.dirs(full.names= F, recursive=F)) {
dir.create('baiduMapFileDrawer')
}
destfile = paste0(lon, ";", lat, ".png")
download.file(url, destfile = paste0("baiduMapFileDrawer/", destfile),
quiet = !messaging, mode = "wb")
if (messaging) message(paste0("Map from URL : ", url))
## read image and transform to ggmap obejct
map = readPNG(paste0("baiduMapFileDrawer/", destfile))
# format file
if(color == "color"){
map <- apply(map, 2, rgb)
} else if(color == "bw"){
mapd <- dim(map)
map <- gray(.30 * map[,,1] + .59 * map[,,2] + .11 * map[,,3])
dim(map) <- mapd[1:2]
}
class(map) <- c("ggmap","raster")
# map spatial info
ll <- XY2LatLon(
list(lat = lat, lon = lon, zoom = zoom),
-width/2 + 0.5,
-height/2 - 0.5
)
ur <- XY2LatLon(
list(lat = lat, lon = lon, zoom = zoom),
width/2 + 0.5,
height/2 - 0.5
)
# ll = as.numeric(rev(geoconv(rev(ll))))
# ur = as.numeric(rev(geoconv(rev(ur))))
attr(map, "bb") <- data.frame(
ll.lat = ll[1], ll.lon = ll[2],
ur.lat = ur[1], ur.lon = ur[2]
)
# transpose
out <- t(map)
out
}
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